Weekly Hydro-meteorological Report, 14, April 2016

Highlights:


Up to 100 mm heavy rainfall was seen in most of south western, western, north western and southern regions of the country during the previous week. Very less rainfall was seen in western districts of the country and the Jaffna Peninsula. NOAA NCEP and WRF models predict a continuation in heavy rainfall in the south western region. MJO is weak so there shall be no effect on rainfall by the MJO. El Niño condition is weakening and neutral conditions are expected by June, July which shall enhance rainfall marginally.
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Summary

Monitoring


Weekly Monitoring:There was heavy rainfall in almost the entire country during the week 6th – 12th April 2016. On the 6th, Ratnapura, Galle, Matara and Kalutara districts received up to 100 mm of rainfall while the surrounding districts and the sea received up to 70 mm. On the 7th Gampaha, Puttalam, Kurunegala and Anuradhapura districts received up to 100 mm rainfall. Then on the 8th a significant reduction in rainfall was seen throughout the country. Only Colombo and Kaluthara districts received rainfall up to 40 mm. On the 9th about 40 mm rain was seen in Gampaha, Kurunegala, Matale and Anuradhapura districts but the sea west of Puttalam received up to 100 mm rainfall. The next two days (10th & 11th) the entire country was mostly dry. Then once again heavy rainfall was seen in Ratnapura, Monaragala and Badulla districts on the 12th where up to 100 mm rainfall was seen.


Monthly Monitoring:During March 2016 most regions of the country received below average rainfall. Rainfall received by Ratnapura, Kaluthara and southern and western parts of Puttalam was about 10 mm/day less than the historical average for this month. Above average rainfall was only seen in Kegalle, Kandy, Matale districts and the southern region of Kurunegala district.

Predictions

14-day prediction:NOAA NCEP models predict up to 45 mm rainfall in each week, during 14th – 20th April and 21st – 27th April in the south western region of the country.

IMD WRF Model Forecast & IRI forecast:According to the IMD WRF model, up to 65 mm rainfall is expected close to Ratnapura and Anuradhapura on 16th and 17th of April. The rest of the country shall receive up to 35 mm rainfall in these 2 days. IRI CFS model predict up to 50 mm total rainfall around Badulla during 13th – 18th April.

Seasonal Prediction:As per IRI Multi Model Probability Forecast for April to June, the total 3-month precipitation shall be climatological. The 3-month temperature has more than 70-80% likelihood in the entire country of being in the above-normal tercile during this period.

PACIFIC SEAS STATE April 14, 2016 :During early April 2016 the tropical Pacific SST anomaly was weakening, and becoming a moderate rather than strong El Niño. All atmospheric variables continue to support the El Niño pattern, but at a somewhat weakened strength. This includes weakened trade winds and excess rainfall in the east-central tropical Pacific, extending eastward more weakly than last month. Most ENSO prediction models indicate continued weakening El Niño conditions during the northern spring season, returning to neutral by late spring or early summer 2016, with a chance for La Niña development by fall.
INDIAN OCEAN STATE :1 degrees C above average sea surface temperature was observed around Sri Lanka.
MJO STATE :MJO is weak and therefore it shall not affect the rainfall.